Tanning process



. ticularly FRANK WA'YLAND, OF SALEM, MASSACHUSETTS.

TANNIN G PROCESS.

No Drawln'g.

To all whom itmay concern:

' Be it known that I, FRANK WAYLAND, a citizen of the United States of America, and resident of Salem, in the county of Essex and State of Massachusetts, have invented new and useful Improvements in Tanning Processes, of which the following is a specification;

This invention relates to a process or method of tanning leather, and more parto such a process whereby the finished leather may have a superficial area much reater than that of the raw hide.

In t e usual'process employed in tanning leather the raw hides, after the preliminary processes comprising liming and unhairing,

are subjected to the act-ion of the tanning liquor, either in a vat or drum, and when the process of tanningis completed the hides are removed from the tan liquor and stretched on frames in the finishing process. As the hides are removed from the tanning solution they have substantially the same or 12% superficial area than when placed therein and this area is usually substantially reduced during the finishing processes by the removal of imperfect portions along the edges. The production of marketable leather in accordance with such practice is thus only about seventy-five feet from a hundred pounds of'cow-hide.

As the supply of light skins for use in the manufacture of shoe uppers,- as well as for automobile and other upholstery use, is entirely inadequate to meet the demand, it has been a common practice of recent years, at least, to form leather of the desired thickness by splitting relatively heavy skins, such as cow-hides, down to the proper weight. Such splitting may be done after the tanning process, but is advantageously performed after. liming and before tanning by means of a machine such as disclosed in the patent to Wayland, 638,368, dated Dec. 5, 1899.

Although by the splitting process the thickness of the heavy hide is reduced so as to adapt it to. uses for which only a relatively light leather is ordinarily suitable, such leather, after the splitting process, still has a superficial area substantially equal to that of the hide from which it was split, the grain or hair side only of the hide being of a quality permissible for use'in high grade work.

In view of the high price of leather and particularly to increase economy in cutting such an irregularly shaped piece of material Application filed November 22, 1920. Serial No. 425,627.

as a hide into pieces suitable for automobile use or or the high shoe tops in vogue at the present time, it would be desirable to stretch the hide whereby to give it as great a superficial area as possible. So far as is known however, no process of stretching a hide before tanning whereby appreciably to in-' crease its area has heretofore been devised. That such a process'is highly desirable will be admitted by anyone skilled in the art and the object of the present invention is to provide a commercially successful process whereby the area of a tanned hide may be made substantially greater than that of the raw hide from which it was made, and without increasing the cost of the tanning process to any appreciable extent.

With this object in View the hide, after the usual preliminary steps of liming and unhairing, is split, either by hand or by a suitable form of splitting machine such as that known to the trade as the Wayland machine, whereby to remove the flesh side. The grain or hair side of the hide, technically known after splitting as the grain is of a somewhat while in this condition may be stretched very easily and to a very considerable amount. The extent to which such grain may be thus stretched will vary according to the kind and quality of hide and Weight or thickness of the grain, but with a light, elastic grain, such as that derived from sheep skin, it is possible to increase the superficial area of the grain from to 100% by so stretching the same'before tanning. In freeing the relativelyelastic and readily stretchable grain from the underlying non-stretchable nerve layer and other material upon the flesh side of the hide, it is obvious that any of the usual processes may be employed. In many cases it is referable, as'above described, to split the hide whereby the flesh side, including the nerve la er is separated 1n a single piece and is available for use in making the cheaper grades of leather but it is substantially immaterial so far as the present invention in its broader aspects is concerned how the nerve layer and the other non-stretchable parts of the flesh side are removed from the grain, the character of the grain belng unaffected even though the non-stretchable portion of the hide be removed in chips as by a shaving process or the like.

In acordance with the present process the gelatinous texture and I grain produced as above described is v,

iti

stretched over a suitable frame of wood or other proper material and secured in its stretched condition to the frame by means of tacks, lacing, or other fastening devices. The stretched grain with its frame is now submerged in a vat or tank containing tan li nor of the desired character, either vegeta is or mineral, and permitted to remain therein until the process of tanning is complete.

llf desired, the leather while still stretched on its frame may be submitted to the processes necessary for softening and finishing the same, and as the leather is already upon the frame the premilinary step, usual in the finishing process of tacking the leather to a frame, is made unnecessary.

By the above process of tanning, however, the mounting of the leather upon frame preliminarly to or during finishing is in many instances found to be unnecesary, as by tanning the leather while taut, it tends to assume a fiat condition which it retains even after removal from the frame, and exhibits little or no tendency to curl or shrink in drying. It is thus possible to work and finish theleather directly from the tanning vat if desired, either upon the tanning frame or after removal therefrom.

The grain, as thus stretched and tanned, retains after finishing substantially the full fore tanning, and thus the finished leather may have an area greatly increased over that of the raw hide.

Notonly is the area of the skin increased but the quality of the leather is also iinproved by the present process. This may be due in part to the drawing out and opening upk of the fibers of the grain side of the hide W ereby they are more completely acted upon by the tanning liquor, thus rendering tne leather of more uniform texture, more flexible and of better appearance and wearing qualities. As a further cause of this improvement in appearance and quality it may be noted that the extreme outer layer on the grain side is ordinarily of looser texture than the underlying fibrous substance and thus the stretching of the two layers to gether tends to take up the slack. so to speak, in the outer layer and brings the fibre of the two layers under substantially equal strain, thus making the outer layer smoother and less subject to the formation of minute wrinkles or ridges. this stretching takes place before tanning, according to this process, the outer and inner layers become relatively fixed by the action of the tanning agent so there is little or tendency to develop wrinkles after the pincess in com plete.

While it may be possible stretch to certaln extent an unsplit hide either unlimed or taken directly from the lime, and while increment of area given it bystretching be-- resume it is comtemplated that such stretching as a preliminary step to the tanning process may be found useful under some circumstances, it is found by experiment that the flesh side of the hide comprising the nerve layer is capable of stretching to but a limited extent and thus, unless removed, serves to limit the stretch of the unsplit hide. By the removal of the flesh side, however, immediately after liming, the grain side is permitted to stretch freely to a great degree as above pointed out.

Although the process as herein described is particularly valuable in the tanning of cow-hide rains, it is to be understood that it might %e employed to advantage in the preparation of leather from skins of other character, such for example as heavy fish skin, if occasion should arise making it desirable so to do.

While lime has been referred to as a suitable unhairing agent, it is to be understood that it has been employed in a generic sense and that otherand well known reagents for preparing the hides for tanning may be substituted therefor without departing from the essential features of the invention.

Having thus described my invention'and the purpose and mode of employment thereof, what l'claim and desire to secure by Letters Patent of the United States is 1. That, process of preparing leather which comprises as steps, separating the grain from the nerve layer of a raw hide, and maintaining such gpain in taut condition while subjecting it to t e action of a tanning reagent for converting it into leather.

2. That process of permanently increasing the superficial area of the grain side of a hide, which comprises separating the grain from the remainder of the hide, stretching such grain wherebysubstantially to increase its area, and subjecting such stretched grain to the action of a tanning reagent while maintaining its increased area-substantially unchanged.

3. That, step in the process of preparing leather which comprises stretching a limed grain previously freed from the nerve layer, whereby substantially to increase its superficial area.

l. The process of preparing leather which comprises as steps, splitting of the hide to remove the fiesh side, stretching the grain thus obtained whereby to increase its area, and

subjecting such rain, while maintaining it in stretched condition, to the action of a tan ning reagent. t

5. The process of preparing leather which which comprises as steps, stretching a gram, 1U

Hill

comprises as steps splitting a limed hide to a remove its flesh surface and stretching the previously freed from the nerve layer, whereby substantially to increase its superficial area, and subjecting such stretched grain to a tannin reagent while maintaining it in its stretc ed condition.

'7'. That process of preparing leather surface of a hide, stretching the grain to increase its superficial area, and maintainlng such grain 1n stretched conditlon while subjecting it to the action of a tanning reagent substantially as described.

8. The process of preparing leather which comprises splitting a limed hide to remove the flesh side, stretching thegrain thus obtained whereby greatly to increase its superficial area, immersing said grain in a tanning solution while malntaining it in stretched condition, and permitting such grain to remain in such solution untilconverted into leather.

9. That process of preparing leather which, comprises as steps, separating the gelatinous and stretchable grainfrom the esh side of a limed hide, stretching such grain to increase its superficial area, and tanning such ain while maintaining it in stretched con ition. i

10. That rocess of preparing leather which comprises the steps of separating the elastic and relatively inelasticlayers of the hide, stretching the elastic portion substantially to increase its superficial area, and

treating said stretched portion to convert it into leather of substantially undiminished area.

Signed by me at Boston, Massachusetts, this twentieth day of November, 1920;

FRANK WAYLAND. 

